code: def test_difference():
      gis = ImageSignature()
      sig1 = gis.generate_signature("test.jpg")
      sig2 = gis.generate_signature(test_diff_img_url)
      dist = gis.normalized_distance(sig1, sig2)
      assert dist == 0.424549547059671
  
file_path: image-match/tests/test_goldberg.py
imports: import pytest
  from numpy import ndarray, array_equal
  from image_match.goldberg import ImageSignature, CorruptImageError
label_desc: Use image node_id 8 for calling a global function with example usage: test_difference() without return types